Paul Ehrlich & Sahachiro Hata's "Magic Bullet": Salvarsan treatment for syphilis

    Paul Ehrlich (1854 - 1915) experimented with a long series of arsenical compounds as a specific treatment for syphilis, in an effort to balance the anti-syphilitic properties with the harmful effects of arsenic on the human nervous system. In cooperation with a visiting scientist from Japan, Sahachiro Hata (1873 - 1938), they demonstrated that the 606th compound in the series, Arsphenamine, commercially marketed after 1910 as Salvarsan, was an effective treatment for the syphilitic spirochaete with few side effects. Ehrlich received the Nobel Prize in 1908 for this and other discoveries. Hata returned to Japan and became his homelands most prominent microbiological researcher.

    Arsphenamine was long believed to believe a dimer with an azobenzene ring attached to two double-bonded As molecules. Almost 100 years after its development, it was discovered to be a mixture of three or five As-azobene molecules linked covalently by single bonds.